The content on this page is being archived for historic and reference purposes only. The content, links, and pdfs are no longer maintained and might be outdated.

Blood Lead Levels in Residents of Homes with Elevated Lead in Tap Water
--- District of Columbia, 2004

The methods and findings in this April 2004 MMWR report have been the subject of continuing interest. In two Notices to Readers, published in the May 21, 2010, and June 25, 2010, issues, CDC has noted limitations of methods employed and the manner in which findings were communicated. Readers should be aware of these limitations, as well as the steps taken to address them.

Lead exposure adversely affects intellectual development in young children and might increase the risk for hypertension in adults (1). In the District of Columbia (DC), of an estimated 130,000 residences, approximately 23,000 (18%) have
lead service pipes (Daniel Lucey, MD, DC Department of Health [DCDOH], personal communication, March 24, 2004).
The Environmental Protection Agency (EPA) requires water authorities to test tap water in 10--100 residences annually for lead.In March 2003, DC Water and Sewer Authority (WASA) expanded its lead-in-water testing program to homes with lead service pipes extending from the water main to the house. By late January 2004, results of the expanded water testing indicated that the majority of homes tested had water lead levels above EPA's action level of 15 parts per billion (ppb). On February
16, DCDOH requested CDC assistance to assess health effects of elevated lead levels in residential tap
water. DCDOH also requested deployment of officers of the United States Public Health Service (USPHS) to assist in the investigations. This report summarizes the results of the preliminary investigations, which indicated that the elevated water lead levels might
have contributed to a small increase in blood lead levels (BLLs). The investigation of elevated water lead levels is ongoing. In the interim, DCDOH has recommended that young children and pregnant and breast-feeding women refrain from
drinking unfiltered tap water (2).

CDC's BLL of concern for children, 10
µg/dL, was adopted in 1991 in response to evidence associating BLLs >10 µg/dL with adverse health effects
(3). Adverse health effects have been reported recently at BLLs <10 µg/dL, particularly in vulnerable populations (e.g., infants and children) (4,5); no safe BLL has been identified
(6). Longitudinal analysis was conducted to identify trends in BLLs in DC before and after changes in the water disinfection process by comparing homes with lead service pipes to homes without lead service pipes. Both the percentage of BLLs
>10 µg/dL and those
>5 µg/dL were examined over time. Cross-sectional analysis of BLLs of
residents in homes with the highest water lead levels was
conducted to determine if residents had BLLs
>10 µg/dL.

Longitudinal Analysis of Childhood Blood Lead Screening Tests

WASA provided DCDOH and CDC with a list of homes (n = 26,141) with lead service pipes. During January
1998--December 2003, the DCDOH blood lead surveillance system recorded 84,929 BLLs. Of these, 43,314 (51%) tests
were venous, and 6,794 (8%) were fingerstick; sample type was not listed on the remaining tests. All blood tests were used in this analysis. For each year of testing, these databases were linked by address. A total of 11,061 BLL laboratory requisition slips listed an address with a lead service pipe.

During 1998--2000, the percentage of BLLs
>10 µg/dL and >5 µg/dL decreased substantially, regardless of the type
of service pipe (Figure). During 2000--2003, the percentage of BLLs >10 µg/dL in persons living in homes known to have
lead service pipes decreased from 9.8% to 7.6% (p = 0.008). The percentage of BLLs
>5 µg/dL in persons living in houses
without lead service pipes continued to decrease, from 22.7% to 15.6% (n = 14,152; p<0.001). However, the percentage of BLLs
>5 µg/dL in persons living in homes with lead service pipes did not decrease statistically significantly (from 696 [32.4%] to
405 [31.2%]; p = 0.34).

Cross-Sectional Study of Homes with >300 ppb Lead in Water

WASA provided the results of lead testing on water samples from 6,170 homes. Of these, 163
(3%)had lead levels >300 ppb in second-draw water collected after a change in water temperature, indicating that some of the lead in the water leached from water pipes outside the home. USPHS officers working in the DCDOH Incident Command structure
contacted residents in the 140 (86%) homes that had telephones and arranged for visits to draw venous samples for BLLs. The
DC Public Health Laboratory determined BLLs by using graphite furnace atomic absorption spectrophotometry for 184
persons in 86households who consented to having blood drawn. Residents were provided with a water filter and information
about reducing lead exposure. In addition, in 12 of the households contacted, 17 persons had a venous blood test
drawn independently and reported to DCDOH since January 2004. These test results also were included in this analysis.

Of the 201 residents from 98 homes with water lead levels >300 ppb tested for BLLs, all had BLLs below CDC's levels of concern (10 µg/dL for children aged 6 months--15 years and 25
µg/dL for adults) (Table). Of the 201 residents, a total of
153(76%) reported drinking tap water, and 52
households(53%) reported using a water filter. On February 26, 2004,
DCDOH sent a letter to all DC homes with lead service pipes, recommending that young children and pregnant and breast-feeding women refrain from drinking unfiltered tap water
(2).

Editorial Note:

The findings in this report indicate that
although lead in tap water contributed to a small increase in BLLs
in DC, no children were identified with BLLs
>10µg/dL, even in homes with the highest water lead levels. In addition, the longitudinal surveillance data indicate a continued decline in the percentage of BLLs >10 µg/dL. The findings in this
report suggest that levels exceedingthe EPA action level of 15 ppb can result in an increase in the percentage of BLLs
>5 µg/dL. Homes with lead service pipes are older, and persons living in these homes are more likely to be exposed to high-dose lead sources (e.g., paint and dust hazards). For this reason, in all years reported, the percentage of test results
>10 µg/dL and the percentage of test results
>5 µg/dL at addresses with lead service pipes were higher than at addresses without lead service pipes.

The findings in this report are subject to at least three limitations. First, the BLL surveillance data include multiple tests on the same person, and persons with lead poisoning are tested more frequently than those with low BLLs. Second,
fingerstick tests are more subject than venous samples to contamination by ambient lead
(7). Finally, neither the blood nor the water
lead test results were collected from a randomized sample. Water was collected from homes with a high probability of having
lead service pipes; the March 2004 BLL screening program was limited to families living in homes with the highest water lead levels, and the routine blood lead surveillance program focused on
identifyingchildren at highest risk for lead exposure.
For these reasons, the percentages of BLLs
>5 µg/dL or >10
µg/dL reported probably are higher than those found in the
general population. However, none of these factors should affect the relative differences between percentage of tests >5 µg/dL by water line type, nor do they explain the change in trajectory of the percentage of tests >5 µg/dL by year after 2000.

The cause of the elevated water lead levels in DC is under review. Although the increase is associated temporally with the change in the disinfection process from chlorine to chloramines that occurred in November 2000, whether this
change contributed to increased lead in the water is unknown.

Because no threshold for adverse health effects in young children has been demonstrated
(6), public health interventions should focus on eliminating all lead exposures in children
(8). Lead concentrations in drinking water should be below the
EPA action level of 15 ppb. Officials in communities that are considering changes in water chemistry or that have
implemented such changes recently should assess whether these changes might result in increased lead in residential tap water. EPA has asked all state health and environmental officials to monitor lead in drinking water at schools and day care centers.
More information about lead poisoning is available from CDC at
http://www.cdc.gov/nceh/lead/lead.htm.

References

Agency for Toxic Substances and Disease Registry. Toxicological profile for lead. Atlanta, Georgia: U.S. Department of Health and Human
Services, Agency for Toxic Substances and Disease Registry, 1999. Available at
http://www.atsdr.cdc.gov/toxprofiles/tp13.html.

District of Columbia Department of Health. Health advisory: lead in
Washington, DC. February 26, 2004. Available at http://www.dchealth.dc.gov.

CDC. Preventing lead poisoning in young children: a statement by the Centers for Disease Control---October 1991. Atlanta, Georgia:
U.S. Department of Health and Human Services, Public Health Service, CDC, 1991.

Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of
Health and Human Services.References to non-CDC sites on the Internet are
provided as a service to MMWR readers and do not constitute or imply
endorsement of these organizations or their programs by CDC or the U.S.
Department of Health and Human Services. CDC is not responsible for the content
of pages found at these sites. URL addresses listed in MMWR were current as of
the date of publication.

DisclaimerAll MMWR HTML versions of articles are electronic conversions from ASCII text
into HTML. This conversion may have resulted in character translation or format errors in the HTML version.
Users should not rely on this HTML document, but are referred to the electronic PDF version and/or
the original MMWR paper copy for the official text, figures, and tables.
An original paper copy of this issue can be obtained from the Superintendent of Documents,
U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800.
Contact GPO for current prices.

**Questions or messages regarding errors in formatting should be addressed to
mmwrq@cdc.gov.